Sending a constant value to the Control logix 5000 registry using Labview via RSLinx

Hi,


I am trying to send a constant value to the PLC..input module using RSLinx OPC server, but the value is being set to 0 and then to user defined value for every 2 secs or so..I thought it was problem with the labview program but..i managed to figure out that it was not the program problem. So it must be a problem with the PLC or the OPC server. If anyone knows how to deal with this problem please let me know.

I am running out of time to complete this..


Thanx for the help in advance

The Input module data in a ControlLogix should always reflect the status of the input points on that Input module.

Don't you think ?

If you're writing data to an Input module's tag, then you're going to see it over-written every time the input module updates. This ought to happen very quickly but maybe there's something about your viewing of the tag that's asynchronous.

Post some specifics about the tagname you're sending data to, and maybe something about the program you're running.

I am trying to send the value to local:7:I.data(which is a DC input module) What I am doing is..I need to switch the servo loop on and then..switch on the movement of the motors for an application. I dont want to use...external switches to do that. So what I am using is the labview to interact with the Registry content using OPC server.

Here I have to send a value to the registry content and the value should remain constant in that registry till I change the value again.

but the value is being set to the value i give but after 1second it is getting back to zero and then again back to user set value.

I dunno what is wrong..

Your OPC application and the controller's own I/O data update mechanism are competing for the value of this tag. The controller is winning.

Instead of attempting to force a value into the input module's tag, write a value into an internal-only tag and use it in parallel with the input bit to run your motion instruction.

Thank you so much for the help, I just figured it out before itself, it was the same technique i have used.

thankyou once again for the help